A vehicle power supply system for, for example, self-starting (starting by starting motor) and kick-starting of motorcycles have been proposed (for example, see JP2002-98032A).
The above conventional vehicle power supply system 1000A includes, for example, an engine control unit 100A and two diodes diode1 and diode2 (see FIG. 7) and requires two external relay circuits relay1 and relay2, resulting in a complicated system configuration.
In the conventional vehicle power supply system 1000A, at self-starting, energization to a motor before switching of the contact of the relay circuit relay2 may unfortunately energize a motor generator through the relay circuit relay1 and blow a fuse fusel. In order to avoid this problem, a user needs to wait for turning-on of the relay circuit relay2 from the time a user presses a starter switch SWS to the time when the energization of a motor M is started, leading to degraded startup performance.
Moreover, in the conventional vehicle power supply system 1000A, at kick-starting, a forward voltage drop of the diode diode1 may reduce a voltage supplied from a power generator (motor generator M) to the engine control unit 100A, unfortunately leading to degraded startup performance at the kick-starting.
Furthermore, the conventional vehicle power supply system 1000A supplies power to an electrical load Load2 (a head lamp H/L, a tail lamp T/L, a stop lamp S/L, a winker lamp W/L) by means of switch elements SWX and SWY to facilitate kick-starting. The electrical load Load 2 is a lamp load having a large inrush current and thus unfortunately, the switch elements SWX and SWY are expensive.